Process of treating vermiculite



June 19, 1934.

O. A. LABUS PROCESS OF TREATING VERMICULITE Filed Oct. 2 1933 a: Q. WWQWCQ/ Patented June 19, 1934 UNITED STATES PATENT OFFICE 14 Claims.

My invention relates to an improved and novel process employed in thetransmutation or chemical transformation of micaceous minerals, such asthose of the vermiculite group, whereby appropriate heat treatment ofsuch a vermiculite ore changes it into a stable, expanded, more or lessplastic, inorganic, highly-cellular material especially adapted for useas a heat-insulating medium.

One of the leading aims of the invention is to provide a process ormethod for the heat treatment of the mineral in a manner hereinafterpresented in detail which has certain distinct advantages resulting in ahighly efficient heating 15 procedure, a greater volumetric yield of thefinished product per unit of mineral heated, a positive control of theheat application to effect complete transmutation of the mineral mass,and a reduction to a minimum of the element of time of go contact of themass with the higher temperatures at which the transmutation or chemicalchange occurs.

The exfoliation, distension or enlargement of various types ofvermiculite by subjecting the mineral to heat at high temperatures,either by the present invention.

By the old methods of operation the mineral is heated at thecomparatively high temperatures at which exfoliation takes place withoutpreliminarily thermally preparing the mineral mass for such treatment orwithout preheating the mineral at temperatures below that at which suchdistension or enlargement occurs to reduce to a minimum the 'heat demandrequired for complete transmutation of the mineral mass with a mini- 0mum interval of] contact of the mass with the heat at high temperaturesconsiderably above that at which exfoliation takes place.

In the methods heretofore practiced by which the mineral at normalatmospheric temperatures and otherwise thermally-unprepared for chemicalmodification or transmutation is subjected directly to elevatedtemperatures considerably above that at which exfoliation occurs,portions of the mineral masses or granules are subjected to excessiveheating before the other particles are sufficiently heated, with theresult that a product is produced which is more or less undesirable foremployment as a heat-insulating medium, because it is more or lessreadily friable and comparatively easily comminuted; and, furthermore,

portions of the mineral mass may be only partially rather thancompletely transmuted.

Under practical operating conditions, the granules of the mineral arenot uniform in size and shape when subjected to the heating processwhich also has undesirable influences on the transmutation operationwhere no consideration is given to reducing the stated inequalities ofthe mineral to be treated.

One of the particular advantages accruing from the employment of myimproved process is the proper and adequate thermal preparation of themineral ore to reduce to a uniform condition the inequalities of heatcontent common with micaceous minerals, especially those of thevermiculite group, directly preceding the heat treatment for itstransmutation through which its enlargement or distension is broughtabout.

The specified mineral in its natural condition contains a variableamount of free moisture and also moisture held by adsorption, both ofwhich moisture contents have a marked influence in the hindrance torapid and uniform heat transmutation of the mineral particles.

It is well known that vermiculite when subjected to heat at hightemperatures exfoliates or swells in large degree, but this phenomenonis not an explosion of the mineral mass being rather a progressiveexfoliation from its outer surfaces to the adjacent, laminated, innermass.

This peculiar or characteristic reaction to heat may be more or lessaptly termed defensive heat resistance, because the outer surfaces ofthe mineral mass which are directly exposed to the heat becomeexfoliated first and form a high resistance to the heat flow into theinner mass of the mineral, due to the fact that these transformed ormodified surfaces are of a highly cellular formation of goodheat-insulation qualities and they assume a color change from theoriginal dark shades of the mineral to a brilliant hue with an addedheat resistance due to reflection.

This combined resistance to rapid, uniform, and complete transmutationof the mineral by the driving off of its water of crystallization or ofconstitution is minimized to a degree where practically only the actualheat to cause such change is the function of the high temperature stageof the new and improved process in which the mineral is first sized andthen preheated at a low heat gradient until the entire mass of allgranules of mineral is brought to a temperature slightly below that atwhich exfoliation begins, which is approximately 300 Fahrenheit, thispreliminary heating driving off the free and adsorbed moisture, whichinitial treatment is distinctly desirable in order to render the processmore expeditious, to secure later maximum expansion of the material andto reduce the friability of the product to a minimum, since the mineralgranules are receptive to heating without the occurrence of theheretofore-stated objectionable resistance.

This preheating stage of my process is subsequently but directlyfollowed by a high-temperature heating characterized by a heat gradientabove the temperature at which exfoliation occurs, but, of course,temperatures in excess of the fusion temperature of the vermiculite areavoided.

The new process may be described more specifically in connection withthe apparatus illustrated in the drawing by means of which it can beconveniently and commercially practiced.

In this drawing:-

Figure 1 is a partial elevation and partial vertical section of theheating appliance;

Figure 2 is a horizontal section on line 2-2 of Figure 1; and

Figure 3 is a horizontal section on line 33 of Figure 1.

The vermiculite mineral reduced to proper size particles, say from ahalf-inch down, is introduced into a hopper 11 from which it is fed overinto the main portion of the furnace by a screwconveyor 12 revolved bypower in any approved manner and rotating in a shell 13 in which thematerial is carried forwardly through the wall 14 of theheater to thecenter of the latter where the shell 13'is fitted withdownwardly-directed delivery-outlet 15 located over the center of a tieror series of concentric, vertically-spaced cones or baflies 16, eachsupported by its legs 17 resting on the corresponding, inwardly-slopingsection 18 of a corrugated inner wall 19 spaced inwardly away from theouter wall 14, thereby providing an annular chamber or jacket 21 betweenthem.

As will be readily understood, the mineral granules deposited by thescrew-conveyor 12 on the center of the uppermost, cone-shaped baflie 16slide down the latter in a thin stream in a diverging path on to thetopmost wall-section 18 which redirects them inwardly in a convergingmanner on to the top of the second cone down which they glide as in thecase of the first cone or bailie on to the next lower wall section 18,and so on down the whole series.

Such tortuous passage or flow of the mineral particles or granulesspreads them out in successive, vertically-spaced, thin, diverginglayers through which the ascending combustion-gases can readily pass andtransmit a portion of their heat thereto, such particles being more orless reassembled by the converging surfaces 18 before each nextdistribution.

The lower portion of the heater or furnace has a combustion-chamber 22directly below and concentric with the lowermost or final distributioncone 116 which is centrally supported from the next cone 16 above in anyapproved fashion, whereby the mineral granules are delivered downwardlyand outwardly into the combustion-compartment in a shallow stream.

As is shown, the combustion-chamber is equipped with a suitable numberof equallyspaced, downwardly and inwardly directed fuelburners 23, 23which project their flames initially into an upper, annular portion 24of the combustion-chamber protected from theincoming mineral by adepending or curtain wall 25.

Such burners receive their air and fuel mixture through appropriatepiping 26 connected to a pair of mixers 27, 27 of proper design andreceiving fuel through conduits 28, 28 and air through pipes 29, 29connected to the top of jacket 21 into which the air is fed by a blower31 and a pipe connection 32 to the lower part of such surroundingjacket.

The bottom of the combustion-chamber 22 delivers the flnished productthrough an opening ture being 275 Fahrenheit.

This assures that all of the particles have been heated uniformlythroughout sumciently to drive off their free moisture and the moistureof adsorption, but without effecting any expulsion of water ofcrystallization or constitution or producing any change in the chemicalcomposition of the mineral.

Nor is the temperature employed sufficient to bring about anysubstantial exfoliation, distension, or swelling of the mineralgranules.

This prevention of excessive temperature in this portion of theapparatus is occasioned by the heat absorbed by the constant stream ofincoming raw mineral and the continuous cooling of the bathe-equippedpreheating flue by the air cooling the jacket around it.

When the mineral is discharged into the lower combustion-chamber it israpidly heated above 300 Fahrenheit adequately to cause quicktransmutation into a somewhat-plastic, foamy, porous or spongy productof much greater volume and correspondingly less density than theoriginal ore.

The combustion gases in .the chamber may be in the neighborhood of 2000Fahrenheit, but this of course does not mean that the mineral itselfreaches such temperature, the mineral by reason of the furnaceconstruction used not coming into contact with the flames directly asthey issue from the burners.

The fact that the preheating and the final heating of the mineral occurin a substantially nonoxidizing atmosphere tends to produce a productwhich is plastic rather than materially friable, as occurs in theordinary vermiculite-calcining process.

One important advantage of the new procedure resides in the fact thatthe initial or preliminary heating of the mineral at a comparatively-lowtemperature rate or gradient prepares the material for maximumtransmutation when subjected to the final high heat because eachparticle then is transformed throughout its mass without encountering asurface change which hinders or retards the necessary internaltransmutation throughout for best results.

The apparatus illustrated and described for practicing the new processis continuous in its operation, but it will be apparent that theprinciples upon which the invention is based are not limited to suchcontinuity of action, since a batch process might be used without, ofcourse, having the advantages which accrue from the employment of thecontinuous process.

It will be readily understood that the required conditions forsatisfactory and efficient practice of the new method can becomparatively easily brought about by regulation of the speed of actionof the conveyors and by controlling the working of the burners, thusestablishing the proper relation between the feed of the mineral and thetemperature of the gases to the heat of which the mineral is subjectedas explained above.

Such control is maintained that the heat in the main heating chamber isonly sufficient to make a materially plastic product, a more or lessfriable material being produced if the degree of heat is excessive.

The plasticity of the exfoliated vermiculite is further favored byreason of the fact that both steps in the heating process are conductedin a substantially non-oxidizing atmosphere composed in part by thegaseous products of combustion and in part by the steam generated by theexpulsion of the moisture from the mineral undergoing treatment.

Additionally, it is to be observed that the heat absorbed by the mineralto effect its transmutation may be of such amount that the temperatureof the gases will have been so lowered that they can be employedimmediately thereafter for the initial preheating step of the process.

The invention is not limited or restricted to the precise and exactdetails of. procedure herein outlined and various changes may beresorted to without departure from the heart and essence of theinvention as defined by the appended claims and without the sacrifice ofany of its material advantages, for example,'instead of employingburners for the combustion of fuel-electric heating may in some cases beresorted to with advantage.

I claim:

1. The process of treating a mineral of the vermiculite group consistingin preliminarily heating the mineral at a sufliciently low temperaturegradient both to heat the mineral and to expel its uncombined moisturebut below the temperature required to drive off its water ofconstitution and then directly thereafter heating such preheated mineralat a relatively-high temperature gradient sufflcient to expel its waterof constitution, whereby to obtain 'a stable, highlycellular productthrough the transmutation of the mineral by the expulsion of such waterof constitution.

2. The process of treating a mineral of the vermiculite group consistingin preliminarily heating the mineral. at a temperature between 212Fahrenheit and 300 Fahrenheit for a sufficient length of time both toheat the mineral and to expel its uncombined moisture and then directlythereafter heating such preheated mineral at a temperature above 300Fahrenheit to expel its water of constitution, whereby to obtain astable, highly-cellular product through the transmutation of the mineralby the expulsion of'such water of constitution.

3. The process of treating a mineral of the vermiculite group consistingin preliminarily heating a continuous stream of the mineral at asufliciently low temperature gradient whereby all of the fully preheatedparticles will have reached a temperature to expel their free andadsorbed moisture but below the temperature required to drive off theirwater of constitution, and substantially immediately thereaftercontinuously heating such fully preheated stream at a relatively hightemperature gradient to quickly convert the mineral particles into astable highly- ,a substantially non-oxidizing atmosphere.

cellular product by the expulsion of their water of constitution.

4. The process presented in claim 1 in which the relatively-hightemperature gradient heating is insufiicient to render the productmaterially friable.

5. The process presented in claim 2 in which the heating above 300Fahrenheit is insufficient to render the product materially friable.

6. The process presented in claim 3 in which the final heating isinsuflicient to render the product materially friable.

'7. The process presented in claim 1 in which all of the heating of themineral takes place in 8. The process presented in claim 2 in which allof the heating of the mineral takes place in a substantiallynon-oxidizing atmosphere.

9. The process presented in claim 3 in which all of the heating of themineral takes place in a substantially non-oxidizing atmosphere.

10. The process of treating a mineral of the vermiculite groupconsisting in preliminarily heating the mineral at a sumciently lowtemperature gradient both to heat the mineral and to expel itsuncombined moisture but below the temperature required to drive off itswater of constitution and then directly thereafter heating suchpreheated mineral at a relatively-high temperature gradient sufficientto expel its water of constitution, whereby to obtain a stable,highlycellular product through the transmutation of the mineral by theexpulsion of such water of constitution, said relatively-hightemperature gradient heating being insufficient to render the productmaterially friable and all of the heating of the mineral taking place ina substantially non-oxidizing atmosphere. I

11. The process presented in claim 1 in which all of the heating iseffected by substantially non-oxidizing gaseous products of combustionbrought into direct contact with the mineral, first to effect theexpulsion of the water of constitution of some of the mineral and thento effect the preheating of other portions of the mineral by the samegases after giving up some of their heat for such expulsion.

12. The process of treating a mineral of the vermiculite groupconsisting in preliminarily heating the mineral at a relatively-lowtemperature gredient to raise its temperature to a point V below butnear the temperature required for its exfoliation and immediatelythereafter heating such preheated mineral at a comparatively-hightemperature gradient to effect its exfoliation.

13. The process presented in claim 12 in which the comparatively-hightemperature gradient heating is insufilcient to render the productmaterially friable.

14. The process presented in claim 1 in which 135 all of the heating iseffected by the combustion of fuel and in which all of the mineralundergoing treatment is subjected to contact with the substantiallynon-oxidizing products of such combustion, the portion of the mineralexposed 1 to the preliminary low-temperature gradient heating being alsosubjected to contact with the steam resulting from the relatively-hightemperature gradient heating of another portion of. the mineral. 4,2145

OTTO A. LAJBUS.

